In India a 3-years trial on potato (Solanum tuberosum L.) was carried out to study the effect of foliar potassium nitrate application on potato yield. On a coarse loamy, non-calcareous soil the application of nitrogen (urea) or foliar KNO3 application showed little effect on potato yield in the absence of potassium application. In presence of potassium, a statistically significant increase in the tuber yield was obtained with increasing level of nitrogen and foliar application of KNO3. Among the 2 foliar fertilizers, i.e. KCl (MOP) and KNO3, potassium nitrate resulted in the highest yield at concentration of 2% which was superior to 1%. The increase in yield levels is related to the increase in the size of the tubers.